Nonfree-tripping overload circuit breaker



Nov. 9, 1948. A. w. KRIEGER NONFREE-TRIPPING OVERLOAD CIRCUIT BREAKER 3 Sheets-Sheet 2 Filed May 10, 1.944

Nov. 9, 1948. A. w. KRIEGER 2,453,235

NONFREE-TRIPPING OVERLOAD CIRCUIT BREAKER Filed May 10, 1944 s Sheets-Sheet s Patented Nov. 9; 1948 NONFREE-TRIPPING OVERLOAD CIRCUIT BREAKER Alvin W. Krieger, Milwaukee, Wis., assignor to Cutler-Hammer, Inc., Milwaukee, Wis., a corporation of Delaware Application May 10, 1944, Serial No. 534,907 7 Claims. (Cl. 200-116) This invention relates to improvements in noniree-tripping overload circuit breakers.

A primary object 01 the invention is to improve the details of construction and the operation of circuit breakers of the aforementioned character.

Another object is to provide novel means for protecting the thermal element against burning out under predetermined overload conditions.

Another object is to provide improved and simplified means for varying the normal degree of sensitivity of the bimetallic thermal element to given overload current conditions, whereby the normal current controlling capacity of the circuit breaker may be reduced to a relatively low value if desired.

Another and more specific object of the invention is to provide a novel form of switch which is operable automatically by the bimetallic thermal element to intermittently shunt the latter in the event ofan overload above a given value. during manual retention of the controlled circuit in closed condition, whereby possibility of destruction of said thermal element is substantially eliminated.

Another object is to provide means for facilitating assembly and support of the bimetallic thermal element with respect to other elements of the device.

Another object is to minimize the number of elements required to secure all parts of the device in assembled relation.

Another object is to provide improved means for effecting attachment of the complete device to a panel or other suitable support.

Another object is to provide novel means atiording an insulating enclosure for certain parts, which are initially exposed to facilitate attachment thereof to each other. v

Another object is to insure a large degree of separation of exposed conducting parts of opposite polarity.

Other objects and advantages of the invention will hereinafter appear.

The accompanying drawings illustrate certain embodiments of the invention which will now be described; it bein understood that the embodiments illustrated are susceptible of modification within the scope of the appended claims.

In the drawings,

Figure 1 is an enlarged vertical sectional view of a circuit breaker constructed in accordance with my invention.

Fig. 2 is a fragmentary sectional view, on the line 2-2 of Fig. 1.

Fig; 3 is a top plan view of the circuit breaker illustrated in Fig. 1.

Fig. 4 is a sectional view, on the line H of Fig. 3.

Fig. 5 is a sectional view, on the line 55 of Fig. 4.

Fig. 6 is a sectional view, on the line 6-6 of Fig. 3.

Fig. 7 is a view, partly in side elevation and partly in vertical section, of a slightly modified form of the'device shown in Figs. 1 to 6, and

Fig. 8 is a fragmentary sectional view, on the line 88 of Fig. 7.

The non-free-tripping circuit breakers herein disclosed are in general of the character described and claimed in my prior Patent No. 2,342,945, granted February 29, 1944, for Circuit breaker. In the devices of Patent No. 2,342,945, however, it was found that upon manual retention of the controlled circuit closed under certain overload conditions of. relatively high value, there was danger of the bimetallic thermal element buming out or fusing, with resultant creation of an unnecessary fire hazard. This is especially true in respect of relatively low capacity'circuit breakers wherein bimetallic thermal elements of small caliber are employed; and the use of an automatically operable switch adapted to periodically shunt the thermal element, as shown in Figs. 1 to 6, hereof, provides for overcoming this difliculty. I

Also in accordance with the disclosure of said Patent No. 2,342,945 four rivets were employed to secure the upper and lower insulating bases to each other, and four additional rivets were molded or embedded in the upper base to provide for rigid attachment of the metal support or cover plate thereto. In accordance with the present invention only four rivets are required to secure said bases and the cover plate in assembled relationship to each other.

Referring first to the circuit breaker shown in Figs. 1 to 6, the numerals l0, H, and I2 respectively designate the metal support or cover plate and the upper and lower molded insulating bases. Plate I0 is punched and stamped to the form thereof illustrated in Figs. 1, 3, 4, and 6; the same having a relatively large centrally located circular opening l3 which is adapted to provide clearance for the intermediate enlargements l4 and I5 upon an operating lever i6 which is essentially like that shown in Patent No. 2,342,- 945. Thus the enlargement I5 consists of a separately formed metal ring having integral diametrically opposed cylindrical lugs l6 and II, which Jointly serve as a pivot for said lever.

Lugs 16" and I! are adapted to seat within open pivotal bearings l8 and 19 formed in the upper surface of base H (see Figs. 4 and 7); said lugs projecting slightly above said surface, and plate l being offset upwardly at and 2| to provide parts of the bearings therefor.

In practice plate I9 is provided with a rectangular upwardly offset portion 22 the flat upper surface of which is coplanar with the upper extremities of offset portions 20 and 29 (as best illustrated in Fig. 7). Such offsets 20, 2| and 22 thus provide a relatively large fiat or coplanar area to seat against the lower surface of a panel or the like (not shown) to which the complete unit may be attached in the manner hereinafter set forth. As best illustrated in Fig. 1, the lower surface of offset portion 22 is so positioned as to provide clearance for element 23 carried by lever I6 upon movement of the latter to its opposite extreme positions.

Element 23 is of substantially inverted U-shape, as best illustrated in Fig. 4; the perforated connecting portion thereof fitting onto a reduced portion of lever i6, which reduced portion is peripherally upset over the inner surface of said connecting portion, as indicated at 24 in Figs. 1

and 4, to rigidly and non-rotatably secure element 23 and ring l5 to lever i6. As shown in Fig. 4 the arms 25 and 26 of element 25 are positioned closely adjacent, but are freely movable with respect to, the opposite side walls of the switch recess 21 which opens to the upper surface of base ll. As shown in Fig. 1, the lower end portions of arms 25 and 26 are of inverted triangle form, the opposite side edges of said triangles being respectively engageable with the walls of the opening 28 between switch recess 27 and the lower recess 29 in which the molded insulating plunger 30 is slidable. Plunger 30 is provided with an enlarged head portion 3! (Fig. 4) which is slidable between and guided by the opposed side walls of recess 29, the relatively narrower lefthand end portion of plunger 36 (Fig. 1) being also slidable between and guided ,by vertical shoulders (not shown) formed upon the walls of recess 29.

Plunger 30 is provided at the head end 31 thereof with a cylindrical recess 32 (Fig. 1) which is adapted to accommodate a coiled compression spring 33 the free outer end of which is adapted to surround a boss or abutment 34 formed upon the vertical arm 35 of an inverted L-shaped metal member, the horizontal arm 36 of said member having a contact tip 31 of fine silver or the like spot-welded or otherwise rigidly attached to the upp r surface thereof, said arm 36 being positioned within a groove 38 in the upper end wall of recess 29 and rigidly attached to base II, as by means of a rivet 39.

The lower end portions of arms 25 and 26 of element 23 are bent inwardly toward each other, as shown at and 4| in Fig. 4, to insure proper engagement thereof with the shoulders formed between the head 3| and the relatively narrower portion of plunger 30.

Also seated in a groove in the upper end wall of recess 29 is the horizontal portion 42 of a punched and formed sheet metal member, said portion being secured to base II as by means of a rivet 43. Portion 42 extends toward the right into alinement with opening 28, and has a forked end the spaced portions 44 and 45 of which are bent upwardly at substantially right angles to provide a fulcrum for an oscillatable contactor 46 to the lower surface of the right-hand end Of Lever I6 is recessed as shown in Fig. 1 to ac-- 'commoda'te an insulating plunger 49 which is biased outwardly from the recess by a coiled compression spring 50. With lever l6 manually moved to the full line position thereof shown in Fig. 1 contactor 46 will be correspondingly moved to and normally held in its circuit completing position as illustrated. Also upon manual or automatic movement of lever IE to its dotted line position plunger 49 will engage the portion 48 of the contactor to move the same with a quick action to its circuit-interrupting or "off position shown in dotted lines.

Plunger 30 is substantially like that shown in said Patent No. 2,342,945, the same being recessed as shown in Fig. 1 to accommodate a vertically positioned coiled compression spring 5| which biases plunger 30 toward the upper end wall of recess 29, and the lower end of said spring sur-' rounds a boss 52 formed upon a relatively thin sheet metal plate 53 to bias the latter downwardly. Plate 53 is provided with notches at the respec-- tive ends thereof for engagement with integral upwardly bent relatively narrow lugs 54 and 55 formed at opposite ends of a relatively thicker sheet metal plate 56. Lug 54 projects upwardly at substantially a right angle to plate 56, and lug 55 extends upwardly and inwardly as shown for cooperation with an angular cam-like wall 51 of the recess aforementioned. Plate 56 is sheared on opposite sides of 2. lug 58 Which is bent down wardly at a predetermined angle as illustrated; and the cut metal edge 59 of lug 58 is located in a substantially vertical plane.

A flat punched insulating plate 60 is interposed between the insulating bases II and I2; plate 56 being slidably movable over the plate 60, and the latter having a relatively narrow slot 6| formed therein to provide just sufllcient clearance for lug 58, the width of which is shown in dotted lines in Fi 4. Slot 5| is made relatively wider at a predetermined point in the length thereof, as indicated at 62 in Figs. 1 and 4, to accommodate the substantially vertical upstanding latch lug 63 which extends upwardly into said enlargement of the slot under normal conditions. -By this means the cooperating lug 58 may be made substantially shorter, and therefore stronger, than the corresponding lug in Patent No. 2,342,945, and the overall depth of the complete device is thereby reduced to a corresponding degree.

Latch lug 63 is formed integrally with a horizontal portion 64 of corresponding width; and portion 64- is spot-welded or otherwise rigidly secured to a rectangular enlargement of corresponding size at a predetermined point in the length of a bimetallic electro-thermally responsive element 65, as indicated at 66 in Figs. 1 and 4.

As shown, the bimetallic element is sup-- ported Within the upwardly opening recess 61 in base l2. The left-hand end 68 of element 65 is enlarged and notched as indicated at 69 and 69 in Figs. 1 and 5. Notch 69 is adapted to fit around the reduced or neck portion 10 of a machined metalmember whose head H is thus adapted to overlie said enlarged end 68. Said metal :member is provided with an externally screw-threaded portion 12 which is adjustable within a threaded passage or opening I8 in the bottom wall of recess 81. The lower end of portion I2 is provided with a keri' ll to provide for adjustment thereof as by means of a screw-driver. wall of recess 81 and the lower surface of enlarged end 88 is a coiled compression spring I5, which biases said end against the lower surface of head II. A countersink or recess 18 surrounds the kerfed end ll of portion I2 to receive a quantity of cement or the like TI to maintain head II in the position to which it has been adjusted at the factory.

The right-hand end of bimetallic element 65 is of enlarged rectangular contour, as indicated at I8, and is interposed between the horizontal portion I8 of an inverted substantially L-shaped sheet metal bus member (preferably a copper strip), the substantially vertical portion of which is designated by numeral 88, and the rectangular portion 8| of a punched and stamped sheet metal contactor the arm of which is designated by numeral 82. Loosely interposed between said portion I8 and the lower surface of plate 88 is the intermediate portion of a pin 83. The parts 18, I8, and 8| are rigidly connected or united,

as by subjecting the same jointly to a spot weld-- ing operation; the pin 83 serving to space said parts a predetermined distance below the upper surface of base I2.

As shown in Figs. 1, 2, and 5, the opposite ends of pin 83 are adapted to fit rather snugly within a pair of opposed vertical grooves 84 and 85 extending downwardly to a plane slightly above the bottom wall of main recess 61 in base I2 (see Fig. 2). Interposed between the bottom wall of main recess 81 and the lower surface of portion 8| of the switch contactor is a coiled compression spring 86, whose lower end surrounds a boss 81 formed integrally with said bottom wall. As best illustrated in Fig. 2, portion 8| of said contactor is provided with downwardly offset lugs 88 and 88, which are also positioned within grooves 84 and 85 respectively; lugs 88 and 88 being of slightly less width than said grooves, to act as a pivot and to permit tilting of contactor 82 in the manner hereinafter described. The insulating plate 68 overlies the pin 83 (Figs. 1 and 2) to limit the upward displacement of the aforementioned parts under the bias of spring 88.

The free end of contactor 82 preferably has attached thereto a tip 88 of fine silver or the like, as by spot welding. Tip 98 is adapted for cooperation with a stationary contact tip 9| of like.

or simiar material; tip 8| being carried at the upper end of a screw or stud 82 which is initially adjustable within the screw-threaded opening through a rivet 83 the rectangular head 94 of which is fitted snugly between the opposed side walls of an auxiliary recess 95 formed in the bottom wall of main recess 81, whereby rotation of said rivet head is positively prevented. Also positioned within auxiliary recess 95 (beneath rivet head 84) is a'punched and stamped sheet metal terminal member, the horizontal portion of which is designated by numeral 86, and the initially vertical portion of which is designated by numeral 91. After downward insertion of portion 81 through a suitable opening 88 in the bottom wall of base I2 and securing of portions 88 and 81 to said base by upsetting the relatively thin-walled lower end of rivet 83, as indicated at 88 in Figs. 1 and 4, the perforated and tapped lower end of portion 81 is bent outwardly at the Interposed between the bottom desired angle to facilitate operation of the wiring terminal screw I88 as by means of a screwdriver.

Attached to the enlarged end 88 of bimetallic element 88, as by spot-welding, brazing, or the like, is a straight portion I8I of a resistanceor heater-wire I82 composed of a suitable material, such as the metal alloy known as Nichrome. Wire I82 is spirally wound in situ around the relatively narrow portion of element 85 between enlargements 88 and 88 in coils of gradually increasing size; as by temporarily positioning the two halves of a split conical mandrel (not shown) on opposite surfaces of said element 65 so that the smaller coils will rather closely surround the left-hand end of said narrow portion and the largest coil will be located adjacent the latch lug 63, a straight or vertical portion I88 being adapted to fit into an opening of suitable size formed in portion 86 of the aforementioned terminal member, as shown in Fig. 1. Portion I88 is spot-welded, brazed, or otherwise mechanically and electrically connected with portion 88, as indicated at I84. By this means any current passing through element 65 is also required to traverse the heater coil I82, whereby element 85 is subjected to the heat of coil I82 to increase the degree of downward bending or deformation of said element under given overload conditions. By employment of the conical coil I82 the degree of radiation of heat therefrom to strip 85 is accentuated and is substantially constant (for given current conditions) in all positions assumed by said strip when in use. For this reason also the strip 85 may be of substantially heavier caliber than would otherwise be possible, while retaining the desired high degree of sensitivity thereof to given values of overload current.

As shown in Fig. 1 the aforementioned sheet metal member which provides the fulcrum or pivotal support for contactor 46 has formed integrally with the horizontal portion 42 thereof a vertical portion I85; insulating plate 68 having a correspondingly shaped rectangular opening (not shown) to provide for downward insertion of portion I85, and the bottom wall of recess 8! in base I2 having a similar opening I88 (see Fig. 5) through which said portion is adapted to extend. Portion I 85 is provided at its lower end with an angular edge l8'I A punched and stamped sheet metal terminal member has a vertical portion I88 (Figs. 1 and '7) which is positioned exteriorly of the lower end of portion I85, the latter and portion I88 having alined openings (not shown) to accommodate the hollow shank of a headed rivet, the end of which shank is upset as shown at I88 to secure said parts'to each other. After said riveting operation a small amount of molten solder (not shown) is applied at the area designated at H8 in Figs. 1 and '7 to insure a rigid mechanical and good electrical connection between said parts. Formed integrally with vertical portion I88 and bent forwardly in a plane parallel to the lower edge I81 of portion I85 is a portion III which is provided with a tapped opening to accommodate the shank of a second terminal screw I88; whereby the axes of both screws are at approximately 45 degrees from the vertical, to facilitate attachment of the circuit wires.

The aforementioned metal cover and support plate I8 is provided adjacent opposite ends thereof with circular openings H2 and H3 to accommodate the reduced hollow neck portions Ill of a pair of like machined resilient locking nuts the intermediate portions II5 of which are preferably of square contour. Extruded or pressed downwardly from plate I are a pair of straight elongated bosses IIB against the outer side edges of which one side of each of the portions are respectively adapted to fit to positively restrain said nuts against rotation. The upper ends'ot neck portions II4 are spun or upset over the upper surface of plate I0, as indicated at III, to rigidly secure said nuts in position. Each nut is initially provided at its lower end with a reduced cylindrical portion which I have designated by the numeral I I8; each nut in its initial form being also provided with a screw-threaded through passage II9 (Fig. 1) of usual form. After the threading operation said portions I I8 of the nuts are each provided with a diametrical kerf or sawcut I20 which extends upwardly throughout substantially the entire length thereof. lhereupon. the parts of each portion IIB separated by kerf I20 are pressed or bent toward each other to provide substantially an inverted frusto-conioal contour thereof, thus reducing the diameter of the lower portion of screw-thread II9 to effect resilient gripping and holding or locking of the threaded shank of a screw or bolt which fits the upper portion of screw-thread H9 in the usual manner. The upper surface of base II is provided at opposite ends thereof intermediate its width with upwardly and endwise opening recesses I2I and I22 (Fig. 1) to accommodate the respective lock-nuts, and to afford access to the heads of rivets 39 and 43. The longitudinal sides of base II remain substantially unbroken and smooth, as best illustrated in Fig. 7.

The device may be associated with a suitable panel (not shown) preferably having a circular opening of slightly larger diameter than opening I3 in plate I0, and a pair of circular openings alined with the threaded passages I I9 in the locking nuts to provide clearance for the shanks of headed clamping bolts or screws (not shown) which are threaded into said passages; such shanks, of course, being of sufficient length to extend downwardly at least a substantial distance into the kerfed and deformed portions I I8 of said nuts.

Assuming that the circuit breaker is connected in series in a circuit to be controlled, by attachment of the wires by means of the pair of screws I00, the same will function normally in substantially the same manner and for the same purposes as set forth in said Patent'No. 2,342,945, That is to say, with lever I6 in the dotted line position thereof shown in Fig. 1, with consequent disengagement of contact tip 41 from tip 31, and with plunger 30 in its extreme left-hand position, manual movement of handle I6 to the full line position thereof illustrated will effect closure or completion of the circuit to be controlled. At the same time the aforementioned arms 25 and 26 will drive plunger 30 toward the right, so that lug 58 will be carried to the right beyond latch lug 63, and upon manual release of lever I6 the edge 59 of lug 58 will engage latch lug 63 (if the bimetallic strip is sufflciently cool to provide for latching positioning of the last mentioned lug), thus restraining plunger 30 against movement toward the left under the bias of spring 33. Under these conditions the contact tip 41 will be permitted to remain in engagement with tip 31 under the bias of switch spring 50. Moreover, under normal conditions the lever I6 of the switch many be manually moved to its opposite 8 extreme positions respectively, to sequentially complete or interrupt the controlled circuit, without requiring'unlatching of the plunger 30.

Closure of switch contacts 41, 31 efl'ects completion of a circuit, which may be traced from the left-hand terminal member III in Fig. 1, through vertical portion I05 and horizontal portion 42 of the aforementioned metal member, through contactor 46 (and tips 41, 31) to and through horizontal portion 36 and vertical portion 35 of the other metal member, by strip through bimetallic element 65, and through heater coil I02 to portions 88 and 8] of the righthand terminal member.

Under given overload conditions bimetallic element 65 will bow downwardly (say to the dotted line position thereof shown in Fig. 1) under the heating effect of the excess current flowing therethrough and through the coil I02; and the latch lug 63 carried downwardly thereby will disengage the edge '59 of lug 58 to normally permit plunger 30 to move to its extreme left-hand position, thus effecting automatic movement of lever I6 and contact tip 41 to the circuit interrupting positions thereof shown in dotted lines in Fig. 1. However, under such overload conditions, if the lever I6 is moved to and/or held in the circuit-completing position thereof shown in Fig. 1 the relatively high current will continue to flow through bimetallic element 65 and heater coil I02, with resultant continued downward bending or bowing of element 65. The switch contactor 82, which is attached to the lower face of the right-hand end of element 65 will continue to move downwardly beyond the dotted line position thereof shown in Fig. 1 (which corresponds to the aforementioned latch-tripping position of element 65) until the tip 90 engages stationary contact tip 9|. When this occurs both element 65 and coil I 02 will be short-circuited, while the controlled circuit is maintained, thus insuring against overheating or fusion of element 65 and/or coil I02, whereby the fire hazard incident to burning out or destruction of such parts (which would be likely to follow in the absence of shorting switch 82, 92) is obviated. As will be understood, when element 65 and coil I02 are thus short-circuited, the former upon cooling will automatically return toward its dotted line position (Fig. 1) with consequent disengagement of contact tip 90 from tip 9|, so that element 65 and coil I02 will again be subjected to the overload current, and after a given length of time (depending upon the degree or value of the overload) tip 90 will again be engaged with tip 9 I, with the result aforedescribed. If the overload disappears or is removed the parts will again assume the normal positions shown in full lines in Fig. 1, so that the controlled circuit will be maintained closed, if desired, without requiring manual retention of lever I6 in its circuit completing position.

As shown in Fig. 1, upon manual adjustment of screw 92 to effect the desired position of tip 9|, a quantity of suitable material (such as molten lead or solder) is deposited in the hollow lower end of member 93 to cover the kerfed lower end of said screw, whereby accidental movement of said screw or further manual adjustment thereof is effectively prevented.

Also as shown at the lower right-hand end of Fig. 1, when the lower ends of portions 35 and 80 have been spot-welded, brazed, or otherwise rigidly connected to each other, I prefer to cover said exposed ends, as by means of a molded insulating member I23, which is recessed at I 24 to freely accommodate said ends. The flat upper edge or surface of cup I23 is attached to the lower surface of base I2 as by means of a suitable adhesive substance. Although I prefer to attach cup I23 in protecting position in the manner just described, it will be apparent to those skilled in the art that a simi ar result could be obtained by reducing one or both transverse dimensions of re-' cess I24 whereby a press fit of cup I23 onto the otherwise exposed ends of the united metal members would be provided.

As shown in Figs. 3, and 6 top plate I0, base II, insulating plate 50, and base I2 are respectively provided adjacent the four corners thereof with alined openings or passages to accommodate, with a rather close fit, the relatively'long shanks I25 (see Fig. 6) of a corresponding number of rivets the heads I26 of which are located in four corner recesses in base I2; two of which recesses are shown at I21 and I28 in Fig. 6. The hollow upper ends of rivets I25 are upset over the upper surface of plate I0, as shown at I29, to rigidly and permanently secure the aforementioned parts in assembled relation. In this manner the required number of fastening elements is only one-half as large a: the number required in the devices of said Patent No. 2,342,945; and, moreover, the necessity for molded-in fastening elements or inserts in the upper insulating base is obviated.

Inthe modification illustrated in Figs. 7 and 8 the lever I6, top plate I0, upper insulating base II, and all of the elements directly associated with said parts may be identical with the corresponding elements aforedescribed. The bimetallic thermally responsive element 65 is in practice of substantlally heavier caliber, and therefore of greater current carrying capacity, than the element 55 aforedescribed. The left-hand end of element 65 is shaped as aforedescribed for cooperation with t e supporting and adjusting elements II, I5, I2, M, etc.. and a filling, of a suitable insulating cement I1 is utilized to retain screw I2 in adjusted position. The lower insulating base I30 differs rightly from the base I2 of Figs. 1 to 6, in that ihe right-hand end of the bottom wall of recess I3I the-rein is closed, as indicated at I32 in Fig.7;

the centering abutment 31 for the coiled spring 85 of Fig. l is omitted from the lower base I30 in Fig. 7: and relatively shallow vertical grooves I33 and I34 are provided in base I30 to accommodate pin 83, as distinguished from the substantially deeper grooves 84 and 85 of base I2 (see Fig. 2). In the device of Figs. 7 and 8 the pin 83 is spotwelded. brazed or otherwise rigidly attached to the upper surface of the right-hand end portion of element 65 whereby said pin acts as a pair of pivot lugs, and pin 33 is biased into engagement with the bottom end walls of grooves I33 and I30 as by means of the resilient, downwardly angled tongue or extension I35 of an inverted U-shaped sheet metal member, one of whose opposite sides is designated by numeral I36 in Fig. 7, and the connecting portion of which is designated by numeral I31. Said sides (see I36, Fig.7) are adapted to fit rather closely but slidably between the opposite side walls of recess I3l in base I30; and the vertical edges of said sides are adapted to fit between pairs of vertical shoulders formed upon the opposed side walls of recess I3I; one pair of said shoulders being shown at I38 and I33 in Fig. '7. Insulating plate overlies connecting portion I31 to retain the same and tongue I35 in proper position. a

A multiple-strand copper wire or bus member I40 has one end thereof spot-welded or otherwise III) rigidly attached to the lower surface of the righthand end of element 65; the other end of bus member I40 being rigidly attached, as by spotwelding, to the lower end portion 35" of a metal member which preferably does not extend downwardly beyond the upper surface of base I30. In other respects portion 35* of the metal member in Fig. 7 corresponds with the aforedescribed portion 35 of the similar metal member in Fig. 1.

In like manner element has spot-welded or otherwise rigidly attached to the upper surface of its left-hand enlarged end portion one end of a multiple-strand copper wire or bus member III; the other end of bus member Ill being similarly spot-welded to the upper surface of-portion. of terminal member 31.

Inasmuch as the aforedescribed shorting switch of Figs. 1 to 6 is not required in the device of Figs. '7 and 8, the aforementioned portion 36 is merely perforated to accommodate the shank 33 of a rivet whose square head 94- is adapted to fit non-rotatably between the straight side walls of a recess, one side wall of which is shown at I42 in Fig '7. The hollow lower end 99 of rivet shank 93 is upset over the lower surface of base I30 to secure terminal member 91 in' assembled position; the head 94 and the upper portion of shank 93 of said rivet being preferably of solid or closed form.

The operation of the circuit breaker shown in Figs. 7 and 8 will be apparent to those skilled in the art; but it may be pointed out that upon connection of the circuit breaker into the circuit to be controlled, and with the switch mechanism in circuit completing'position (as indicated by the position of lever I6), the lever I6 when manually released will provide for maintenance of the controlled circuit pending a given degree of downward bending or bowing of bimetallic element under overload conditions of predetermined value. Also, as in my Patent No. 2,342,945, the controlled circuit may be interrupted or completed at any time at will, whether or not the circuit is subjected to overload conditions. That is to say, the circuit breaker is of the non-free-tripping type.

In each form of circuit breaker herein disclosed the means for supporting the bimetallic element (65 or 55) have been improved to provide for easier assembly thereof than in my aforementioned Patent No. 2,342,945, while at the same time effecting a reduction in the degree of variation of the operating characteristics of the breakers resulting from normal manufacturing tolerances.

I claim:

1. In a non-free-tripping electro-thermally responsive overload circuit breaker, in combination, a switch included in the circuit to be controlled, said switch having a single pivoted lever normally operable manually to effect completion or interruption of the controlled circuit at will in the absence of overload conditions, a reciprocable plunger spring-biased to effect circuit interrupting operation of said switch, a bimetallic strip normally included in circuit with said switch, said strip and said plunger having cooperating latch members to restrain said plunger against its bias upon initial closure of said switch, said bimetallic strip being supported at each end against substantial outward longitudinal movement whereby the same is adapted to buckle or bow between said ends as an incident to overload conditions in the controlled circuit, whereby upon attainment of an overload condition of given value said latch members are automatically disengaged to thereby tend to effect interruption of the controlled circuit, said lever being manually operable at will to insure completion of said circuit regardless of said overload conditions, an auxiliary switch associated with said strip and operable automatically thereby during manual maintenance of said circuit under overload conditions, said auxiliary switch comprising a fixed contact, and a substantially rigid sheet metal contactor attached to one end of said strip and adapted upon a given degree of bowing of the latter under overload conditions to engage said contact to thereby effect temporary short-circuiting of said strip whereby the possibility of fusion of the latter is substantially eliminated.

2. In a non-free-tripping electro thermally responsive overload circuit breaker, in combination, a switch included in the circuit to be controlled, said switch having a single pivoted lever normally operable manually to effect completion or interruption of the controlled circuit at will in the absence of overload conditions, a reciprocable -plunger spring-biased to effect circuit interrupting operation of said switch, a bimetallic strip normally included in circuit in series with said switch, said strip and said plunger having cooperating latch members to restrain said plunger against its bias upon initial closure of said switch, said bimetallic strip being supported at each end against substantial outward longitudinal movement whereby the same is adapted to buckle or bow between said ends as an incident to overload conditions in the controlled circuit, whereby upon attainment of an overload condition of given value said latch members are automatically disengaged to thereby tend to efiect interruption of the controlled circuit, said lever being manually operable at will to insure completion of said circuit regardless of said overload conditions, an auxiliary switch associated with said strip and operable automatically thereby during manual maintenance of said circuit under overload con- 12 and said plunger having cooperating latch members to restrain said plunger againstits bias upon initial closure of said switch, said bimetallic strip being supported at each end thereof against substantial outward longitudinal movement whereby the same is adapted to bow downwardly between said ends as an incident to overload conditions in the controlled circuit, whereby upon attainment of an overload condition of given value said latch members are automatically disengaged to thereby tend to effect interruption of the controlled circuit, said lever being manually operable at will to insure completion of said circuit regardless of said overload conditions, an auxiliary switch associated with said strip and operable automatically thereby during manual maintenance of said circuit under overload conditions, said auxiliary switch comprising a fixed contact, a substantially rigid sheet metal contactor attached to one end of said strip and adapted upon a given degree of bowing of the latter under overload conditions to effect temporary short-circuiting of the same and said heater coil whereby the possibility of fusion of said parts is substantially eliminated.

4. In an overload circuit breaker of relatively low capacity, the combination with a bimetallic electro-thermally responsive strip, of a spirally wound heater coil connected in circuit in series with said strip, said coil being of approximately cone-shape, the small end portion of said coil being located adjacent one end of the strip whereby a relatively high degree of heating of said strip by said small end portion of the coil is insured, and the large end of said coil being located at an intermediate point in the length of said strip to. accommodate the latter without contact when in bowed condition.

5. In an overload circuit breaker of relatively 40 low capacity, the combination with a switch havditions, said auxiliary switch comprising a fixed contact, a substantially rigid sheet metal contactor attached to one end of said strip and adapted upon a given degree of bowing of the latter under overload conditions to effect temporary short-circuiting thereof, whereby the possibility of fusion of said strip is substantially eliminated, and said bimetallic strip being so constructed and arranged that upon cooling thereof to a predetermined degree after each shor-t-circuiting thereof said auxiliary switch is automatically reopened to temporarily remove said short-circuit, the aforementioned parts acting to continue said cycle of operations pending opening of saidfirst mentioned switch or a predetermined reduction in value or removal of said overload conditions.

3. In a non-free-tripping electro-thermally responsive overload circuit breaker, in combination, a switch included in the circuit to be controlled, said switch having a single pivoted lever normally operable manually to effect completion or interruption of the controlled circuit at will in the absence of overload conditions, a reciprocable plunger spring-biased to eflect circuit interrupting operation of said switch, a bimetallic strip normally included in circuit in series with said switch, a heater coil surrounding a portion of the length of said bimetallic strip, one end of said coil being electrically and mechanically v connected with one end of said strip to form a part of the series circuit for the latter, said strip ing a single manually operable member, of a bimetallic electro-thermally responsive strip, a spirally wound heater coil connected in circuit in series with said strip, said coil being of approximately cone-shape, the small end'portion of said coil being located adjacent one end of the strip whereby a relatively high degree of heating of said strip by said small end portion of the coil is insured, the large end of said coil being located at an intermediate point in the length of said strip to accommodate the latter without contact when in bowed condition, an auxiliary switch including a contactor carried by said strip and movable automatically to a degree corresponding to the degree of bowing of the latter, and a stationary contact engageable by said contactor under given conditions to temporarily eilect short-circuiting of both said strip and said heater coil.

6. In an electro-thermally responsive overload circuit breaker, in combination, a switch included in the circuit .to be controlled, a single manuallyoperated lever whereby said switch is normally operable to effect and maintain completion or interruption of the controlled circuit at will in the absence of overload conditions, means springbiased to effect interruption of the circuit controlled by said switch, a single bimetallic strip normally included in circuit with said switch, said strip and said spring-biased means having cooperating latch members to restrain said means against its bias, said bimetallic strip being so supported at each end that the same is adapted to buckle or bow between said ends as an incident to current passage in the controlled circuit,

l3. whereby upon attainment of an overload condition of predetermined value said latch members are automatically disengaged to thereby tend to eiiect interruption of the controlled circuit, said switch being manually operable at will by said lever to insure completion of said circuit regardless of said overload conditions, and an auxiliary switch associated with said strip, said auxiliary switch comprising a substantially rigid sheet metal contactor attached to one: end of said strip and adapted upon a given degree of bowing oi the latter during manual maintalnance of said circuit under overload conditions to effect temporary short-circuiting of said strip.

7. In an electro-thermally responsive overload circuit breaker, in combination/a switch included in the circuit to be controlled, a single manually operable lever whereby said switch is normally operable to effect and maintain completion or interruption of the controlled circuit at will in the absence of overload conditions, means springbiased to eflect interruption oi the circuit controlled by said switch, a single bimetallic strip normally included in circuit in series with said switch, said strip and said spring-biased means having cooperating latch members to restrain said means against its bias, said bimetallic strip being so supported at each end that the same is adapted to buckle or bow downwardly between said ends as an incident to current passage in the controlled circuit, whereby upon attainment of an overload condition oi predetermined value said latch members areautomatically disengaged to thereby tend to eiiect interruption of the controlled circuit, said switch being manually operable at will by said lever to insure completion 0! said circuit regardless of said overload conditions,

4 an auxilliary switch associated with said strip, said auxiliary switch comprising a substantially rigid sheet metal contactor attachedto one end of. said strip and adapted upon a given degree of bowing oi the latter during manual maintenance 01' said circuit under overload conditions to effect temporary short-circuiting oi. said strip, and said strip being so constructed and arranged that upon cooling thereof to a predetermined degree after each short-circuiting oi the same it will automatically eflect reopening of said auxiliary switch to temporarily remove said short-circuit, the aforementioned parts acting to continue said cycle 01' operations pending opening of said first mentioned switch or a predetermined reduction in value or removal of said overload conditions.

ALVIN W. KRIEGER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,271,558 Francis July 9, 1918 1,966,444 Guett July 17, 1934 2,049,354 Chapman July 28, 1938 2,097,775 Pittman et al Nov. 2, 1937 2,239,829 Pittman et a1 Apr. 29, 1941 2,255,169 Ireland Sept. 9, 1941 2,280,960 Lee Apr. 28, 1942 2,293,179 Swingle Aug. 18, 1942 2,342,945 Krieger Feb. 29, 1944 2,347,014 Willmann Apr. 18, 1944 2,857,151 Von Hoom Aug. 29, 1944 2,390,947 Koci Dec. 11, 1945 2,419,072 Hall Apr. 15, 1947 

